Field of Invention
The present invention relates to a noise-shielded capacitive touch device; particularly, it relates to such noise-shielded capacitive touch device capable of effectively isolating two sensor regions to avoid cross interferences.
Description of Related Art
Please refer to FIG. 1A, which shows a top view of a conventional capacitive touch device. The conventional capacitive touch device 10 shown in FIG. 1A is for example a mutual capacitance type touch panel which comprises multiple sensor regions. In the shown example, the capacitive touch device 10 comprises a first sensor region 11 and a second sensor region 12, wherein each of the first sensor region 11 and the second sensor region 12 is, for example, a capacitive touch sensor. Each of the first sensor region 11 and the second sensor region 12 includes plural driving lines DA1˜DA9 in parallel along a first direction and plural sensing lines SA1˜SA9 in parallel along a second direction, wherein the first and second directions are orthogonal to each other. Sensing nodes N11, N12, N13. . . , N98, N99 are provided at the intersections of the driving lines DA1˜DA9 and the sensing lines SA1˜SA9. The so-called mutual capacitive sensing method is to monitor the change of the capacitance at each of the sensing nodes N11, N12, N13. . . , N98, N99 in the sensor regions 11 and 12 of the capacitive touch device 10. For example, if each of the first sensor region 11 and the second sensor region 12 includes J driving lines and K sensing lines, then a total of (J×K) sensing nodes are formed in each sensor region. During operation, each of the driving lines DA1˜DA9 is supplied by a driving voltage, and the charges of the driving lines DA1˜DA9 are capacitively coupled to the corresponding sensing lines SA1˜SA9 at each of the intersections (i.e., the sensing nodes N11, N12, N13. . . , N98, N99) to generate corresponding voltages sensible by the sensing lines SA1˜SA9. For example, as shown in FIG. 1A, each of the first sensor region 11 and the second sensor region 12 includes 9 driving lines DA1˜DA9 and 9 sensing lines SA1˜SA9, thereby forming a total of 81 individual and spatially separated sensing nodes N11, N12, N13. . . , N98, N99 in each sensor region. When the capacitive touch device 10 is touched, a capacitance of a node that corresponds to the location of the touch changes, and the voltage sensed by a corresponding sensing line SA1˜SA9 changes accordingly. Thus, the capacitive touch device 10 can sense touches.
Please refer to FIG. 1B, which shows a cross-sectional view of the conventional capacitive touch device 10. As shown in FIG. 1B, the capacitive touch device 10 further comprises a substrate 14. The plural sensing lines SA1˜SA9 of the first sensor region 11 and the second sensor region 12 are disposed at one side of the substrate 14, and the plural driving lines DA1˜DA9 of the first sensor region 11 and the second sensor region 12 are disposed at an opposite side of the substrate 14. In such configuration, an intersection of a driving line (e.g., DA9) and a sensing line (e.g., SA9) forms a sensing node (e.g., N99) as shown in FIG. 1A. The term “intersection” is used from top view perspective, indicating a location where one of the driving lines DA1˜DA9 and one of the sensing lines SA1˜SA9 “cross” or come nearest each other in their respective planes. From the perspective of cross-sectional view, the driving lines DA1˜DA9 and the sensing lines SA1˜SA9 do not directly contact one another; instead, they are capacitively coupled to one another at two sides of the substrate 14 at the intersections.
In the first sensor region 11 and the second sensor region 12, for example, the driving line DA9 and the sensing line SA9 are capacitively coupled to each other at the sensing node N99. That is, because the voltage level of the driving line DA9 is different from that of the sensing line SA9, a magnetic field line is formed at the sensing node N99. However, because the distance between the first sensor region 11 and the second sensor region 12 is short, a magnetic field line can also be formed between the driving line DA9 of the first sensor region 11 and the sensing line SA9 of the second sensor region 12, thus creating an interference between the first sensor region 11 and the second sensor region 12. A signal in one of the first sensor region 11 and the second sensor region 12 becomes a noise in the other sensor region.
To overcome this drawback, certain prior art proposes to dispose a shielding layer 13 between the first sensor region 11 and the second sensor region 12. More specifically, a large area shielding layer 13 is disposed on the same plane as the driving lines DA1˜DA9. Preferably, the shielding layer 13 is substantially grounded (i.e., the shielding layer 13 is at or near a 0V electric level), or connected to a known electric level. The shielding layer 13 provides an electric field to attract undesired magnetic field lines, thus reducing the interference of noises. For example, some magnetic field lines will be formed between the driving line DA9 of the first sensor region 11 and the shielding layer 13 instead of between the driving line DA9 of the first sensor region 11 and the sensing line SA9 of the second sensor region 12. Nevertheless, this solution requires a great modification of the layout and it significantly enlarges the size of the device. In addition, the large area shielding layer 13 still can not completely avoid cross interferences between the first sensor region 11 and the second sensor region 12 (i.e., as shown in FIG. 1B, even though a large area shielding layer 13 is provided, a magnetic field line can still be formed between the driving line DA9 of the first sensor region 11 and the sensing line SA9 of the second sensor region 12, hence still resulting in undesirable cross interferences between the first sensor region 11 and the second sensor region 12.
In view of the above, to overcome the drawbacks in the prior art, the present invention proposes a noise-shielded capacitive touch device capable of effectively isolating two sensor regions to avoid cross interferences.